The formation of the Antarctic ice sheet continues to puzzle scientists but one group may be close to solving the ice sheet mystery.

A team of scientists from Cardiff University’s School of Earth and
Ocean Sciences and Amgueddfa Cymru - National Museum Wales travelled to
Africa to find new evidence of climate change which helps explain some
of the mystery surrounding the appearance of the Antarctic ice sheet.

Ice
sheet formation in the Antarctic is one of the most important climatic
shifts in Earth’s history. However, previous temperature records show
no evidence of the oceans cooling at this time, but instead suggest
they actually warmed, presenting a confusing picture of the climate
system which has long been a mystery in palaeoclimatology.

Now
Dr Carrie Lear, Lecturer in Palaeoceanography, and her team at Cardiff
have presented new temperature records using ancient sea floor mud
recovered from Tanzania, East Africa. The shell chemistry of pin-head
sized animals called foraminifera (“forams”) reveal that ocean
temperatures did in fact cool by about 2.50C.

Dr Lear said:
“Forams are great tools for studying climates of the past, which helps
us learn about the uncertainties of our future greenhouse climate.
These new records help resolve a long-standing puzzle regarding the
extent of ice-sheet growth versus global cooling, and bring climate
proxy records into line with climate model simulations.

“We
have been able to use the chemistry of the Tanzanian microfossils to
construct records of temperature and ice volume over the interval of
the big climate switch. These new records show that the world’s oceans
did cool during the growth of an ice sheet, and that the volume of ice
would have fitted onto Antarctica; so now the computer models of
climate and the past climate data match up.”

The team at
Cardiff University’s School of Earth, Ocean and Planetary Sciences will
now look for evidence of the ultimate cause of the global cooling using
the forams. They believe the prime suspect is a gradual reduction of
CO2 in the atmosphere, combined with a ”trigger’ time when Earth’s
orbit around the sun made Antarctic summers cold enough for ice to
remain frozen all year round.